For some reason in the past few years, Hollywood movies have started giving away every plot point that's in their movies... IN THE GODDAMN TRAILERS. Every trailer has become a minefield; if you go too far into a trailer, you will see the entire movie in sequential order. This will include all the best plot twists, character arches, action sequences and surprises. You don't even have to see the movies anymore! They'll take you deeply through every emotion by the end of the 3 minutes... you'll feel excited, shocked, scared, sad, intrigued and by the end of it you'll have grown as a person... leaving you no urges to watch the actual movie.
Attention spans are getting shorter. 130 years ago, the first films showed random people walking down the street and everyone was amazed. Since then, attention spans have gone to shit. Now, if your video isn't spectacular in the first 10 seconds... actually, let’s say the first 3 seconds, viewers will click OFF of your video and go watch a BuzzFeed video instead.